A. Field of the Invention
The present invention relates to fish feeding systems and, in particular, to a system which provides automatic control of the feed rates to fish.
B. Discussion of the Prior Art
U.S. Pat. No. 4,359,014 to Molaug, et al. describes a food dispensing system which intermittently dispenses food to fish based upon the oxygen content of water in a tank within a plurality of tanks.
U.S. Pat. No. 4,027,627 to Fillion describes a feeder comprising a hopper with an impeller to direct a broadcast feed from the hopper with an associated timing mechanism utilized to provide interval feeding from the feeder in to a fish pond.
U.S. Pat. No. 3,368,529 to Ferris describes a feeding system for cows which has individually adjustable rate of feed positions.
U.S. Pat. No. 3,113,556 to Jarvis describes an automatic fish feeder having an auger which is controlled by a motor and timer. The feeder has the capability of continuously feeding fish in a tank for 24 hours per day over a period of a number of months.
Intensive aquaculture systems operate with two fish husbandry fields of thought. The first is for small fish. This husbandry practice occupies about 1/4 of the farm but takes the most management time. A series of tanks of water are provided. The tanks contain respective groups of fish of different sizes. The water exchanges about 3 times per hour i.e. (new water in and old water out). Thus, for example a fish tank of water would contain the fishlings of a very young age, while successive tanks each contain a group of fish of bigger and bigger size until a last tank contains fish big enough to compete with market size, viz., the adult fish.
Each small fish group is fed a different size food by the feeder and the feeding rate is increased by speeding up the motor as the fish grow. Fish can stay in a tank group until the biomass capacity of the tank is reached for the group. The biomass capacity is a number of fish pounds or number of fish determined by the critical gas levels in the water (such as oxygen), the water quality (which is lowered by fish body excretions and excess feed), and the fish size (metabolism rate). When the tank biomass capacity is reached, the fish population must be divided into another tank and typically a larger size feed can be fed by a different spring to the now larger fish. The fish are always fed the largest sized feed possible to minimize impact on the water quality.
When the fish reach a size that they can eat the largest sized food pellet (about 7 inches with trout) a different husbandry is practiced. The small fish are mixed with the larger fish until the biomass capacity of the tank is approached. Then with frequent harvesting of the big fish for markets and with the younger fish growing larger it is possible to achieve the tank biomass limits constantly. The benefits of this are maximum production per capital investment in the farm.
Another benefit of continuous feeding is the balance established in the tank which bears on fish stress, feed utilization, fish excretions into the water and the use of gases (such as oxygen) in the water. This balance provides management benefits to the farm since all mature tanks are treated alike and system capacity is a maximum.
If larger fish were managed in size groups as younger fish are managed there would be constant management problems of how and where to feed and inefficient system utilization. If batch or interval feeding of fish is done in a system with a biomass near capacity, large stress variations occur on the fish due to fluctuations in the oxygen gas levels in the water. Thus, economies of capital and operation endorse continuous feeding of fish.
The above prior art fails to teach such a fish feeding system which operates to continuously feed the fish during the daylight hours and to maintain a balance of the amount of oxygen available for the fish.